Currently, a so-called “virtual Digital Media Server (vDMS)” is known. One of the examples of the vDMS is TVersity Media Server, information about which may be found at http://tversity.com/. The vDMS is located between a content server and a Universal Plug and Play (UPnP)-enabled Digital Media Player (DMP), and provides the UPnP-enabled DMP with a UPnP Content Directory Service (CDS) regarding the content server. In other words, the UPnP-enabled DMP can obtain a content list of a content server via the vDMS.
In addition, an IP Multimedia Subsystem (IMS) Gateway (IG), which is a kind of a User Equipment (UE), is known. The IG works as a Session Initiation Protocol (SIP) Back-to-back User Agent (B2BUA) and provides IMS-incapable devices (e.g., DMPs) with IMS connections. A basic configuration of an IG is proposed in, for example, WO 2006/045706.
If the vDMS cooperates with the IG, the vDMS can provide a DMP with a content list of a content server via an IMS network. In other words, a combination of the vDMS and the IG enables the DMP to obtain the content list of the content server via the IMS network. In this scenario, a DMP first obtains a content list of a content server via the vDMS. When a certain content item is selected from the content list by a user, the DMP sends an HTTP GET message to the content server storing the selected content item in order to retrieve it. It should be noted that the HTTP GET message and the selected content item are exchanged between the DMP and the content server without going through the vDMS and the IMS network.
Recently, content stored by a content server is often protected by means of a Digital Rights Management (DRM) technology such as Open Mobile Alliance (OMA) DRM 2.0. In the case of OMA DRM 2.0, a DMP receives a content item in the form of DRM Content Format (DCF). If the DMP receives a DCF content item, it acquires from a Rights Issuer a Rights Object (RO), which enables reproduction of the DCF content item, by means of OMA DRM Rights Object Acquisition Protocol (ROAP). When an RO is requested, the Rights Issuer authenticates the DMP based on the DMP's device certificate. Similar to the case of a content item, an RO is sent from a Rights Issuer to a DMP without going through the vDMS and the IMS network.
Content providers often require the charging of a user of a DMP for consumption (typically, reproduction) of content. In particular, content providers often require that an IMS operator carry out charging on their behalf because the IMS operator usually has information regarding the user, which is sufficient to facilitate charging.
However, because content items and ROs are received by a DMP without going through the vDMS and the IMS network as described above, it is quite difficult or impossible for the IMS operator to identify who consumed a given content item. Consequently, it is impossible for content providers to efficiently and appropriately charge users.